Rotary to linear drive mechanisms are known. In each, a threaded nut or the like is adapted to be translated back and forth, or up and down, relative to a screw member which rotates. The nut may be adapted to lift car windows and antennas, to remotely actuate building windows and engine controls, and, in short, wherever it is desirable and feasible to effect linear motion of a member from rotary motion of another member.
Non-flexible rotary to linear drive mechanisms are often roller-type or ball-type and frequently include ball screw cylinders employing various types and configurations of non-flexible screw members, or other type nut and screw devices requiring complicated components.
Prior art flexible rotary to linear drive devices generally employ a separate wire coiled helically about a flexible core. Such devices tend to be difficult to fabricate and often require many special parts.
The present invention employs a conventional rotatable flexible shaft except for its outermost layer of coiled windings. Thus, the machine for winding the respective layers of windings is adapted to wind the outermost layer, not continuously closely coiled as in the layer or layers of windings underneath the outermost layer, but in an identical series of continuously closely coiled windings, each adjacent series thereof having a gap therebetween formed by an absence of windings, the gaps thus forming a continuous helical path along the length of the flexible shaft. The depth of the helical gap is substantially equivalent to the diameter of the wire used for the outermost layer of windings. The width of the helical gap is determined by the number of absent or missing coils or turns of windings between the series of continuously coiled windings. The pitch of the gap is controlled by the number of windings in any of the closely coiled series of windings.
The smooth-bored nut which travels along the helical gap is provided with a pair of spaced pins extending into the smooth bore and engaging the helical gap at two points therealong defined by its pitch. Upon rotation of the shaft, the nut will be routed therealong, even though the shaft is curved or tortuously disposed and of virtually unlimited length.
The present device is simple and inexpensive to fabricate.